This invention relates to a novel vessel or envelope structure which is adapted for use in the manufacture of cathode ray tubes and the like. More particularly, the invention relates to a color television tube which sustains itself against very low internal pressure.
In FIG. 1, a prior art color television tube 10 is illustrated schematically. A panel 11, a funnel 12 and a neck 13 are each formed and fused together in a conventional manner. A pin and gun support 14 is inserted in an open end 15 of the neck 13 and sealed therein. The entire tube 10 is evacuated in a conventional manner and one of various implosion protection devices may be used, such as a shrink fit band (not shown) or an epoxied rim band with a compression device located thereover known as a tension or "T" band 16. Shrink fit and "T" bands are compressively disposed about the perimeter of the panel 11 in one of various ways known in the art. Reference will be made to the "T" band 16 hereinafter for convenience only and it should be understood that other implosion protection devices of its type may be used. A force f represents a destructive impact on the panel 11 and the T band 16 exerts a radial force on the panel 11 in order to reduce the propagation of cracks caused by the destructive force f so that the tube 10 slowly devacuates in a manner which will prevent implosion.
Recent developments in the picture tube art have permitted manufacturers to increase the size of TV picture tubes substantially. As the size of television tubes increases, the size, strength, and complexity of the T band arrangement must be greatly increased. For example, a test conducted by Underwriters' Laboratories Inc. subjects the frontal portion of the panel 11 to an impact of about 15 foot pounds delivered by a five pound missile. The amount of energy dissipated by the panel 11 is sufficient to destroy the tube so that glass fragmentation can be observed. Because of the nature of the test, it is necessary to design implosion protection systems to insure successful results should an implosion occur during normal use. This design requirement becomes increasingly difficult with the larger tubes since the evacuated space within the tube 10 and the stresses on the panel face 11 are progressively increased by the larger surface area of the panel 11.
Thus, the present invention has been made in order to supplement the conventional TV implosion protection devices, e.g., the T band 16 and others, in such a way that a reliable outgassing or devacuation of the tube will occur without the necessity of increasing the hardware required for the conventional implosion protection.